Fiber-based strain sensors and method of manufacturing the same
The present exemplary embodiments propose a fiber-based strain sensor including: at least one first electric conductive line including a first flexible part having electric conductivity and at least one second electric conductive line which is woven to be in partially contact with the first electric conductive line, includes a second flexible part having electric conductivity, and is implemented to conduct electricity with the first flexible part having electric conductivity in a stretched state.
1 . A fiber-based strain sensor comprising:
at least one first electric conductive line including a first flexible part having electric conductivity; and
at least one second electric conductive line which is woven to be in partial contact with the at least one first electric conductive line, including a second flexible part having electric conductivity, and being implemented to conduct electricity with the first flexible part having electric conductivity in a stretched state,
wherein the at least one first electric conductive line and the at least one second electric conductive line form a physical structure comprising: a conductive part having electric conductivity formed by depositing metal nano particles inside the first flexible part and the second flexible part; and an insulator formed by depositing an insulating thin film on a surface of the conductive part,
wherein the at least one first electric conductive line and the at least one second electric conductive line are implemented with a negative gauge factor (N-GF) configured such that current flows as the at least one first electric conductive line and the at least one second electric conductive line directly contact each other through a crack formed by the insulator only in the stretched state, and
wherein a degree of causing a crack according to strain is adjusted by the insulating thin film having a preset modulus, thickness, or hardness through a curing process by selective irradiation of ultraviolet curing (UV-curing).
2 . The fiber-based strain sensor according to claim 1 , wherein the at least one first electric conductive line and the at least one second electric conductive line are woven to be twisted and a first node connected to the at least one first electric conductive line and a second node connected to the at least one second electric conductive line forms a mutual resistance which is formed to be equal to or lower than a predetermined resistance according to a stretched state.
3 . The fiber-based strain sensor according to claim 2 , wherein a degree of resistance change is adjusted by adjusting a number of times of twisting the at least one first electric conductive line and the at least one second electric conductive line or a degree of twisting the at least one first electric conductive line and the at least one second electric conductive line.
4 . The fiber-based strain sensor according to claim 2 , wherein the first flexible part and the second flexible part include at least one of polyurethane, styrene-butadiene-styrene (SBS), styrene butadiene rubber (SBR), and polydimethylsiloxane (PDMS) which are formed of polymer materials and the conductive part includes at least one of metal material implemented by nano particles, a conductive organic material, and nano materials.
5 . The fiber-based strain sensor according to claim 2 , wherein the insulator includes at least one of organic materials which form an insulator characteristic, such as SU-8, polyimide, PVA, PMMA, or CYTOP or oxide, such as SiOx or HfOx.
6 . The fiber-based strain sensor according to claim 2 , wherein the insulator adjusts a degree of causing a crack according to strain, by adjusting a modulus, a thickness, or a hardness by means of curing.
7 . The fiber-based strain sensor according to claim 1 , wherein the fiber-based strain sensor is implemented to be applied to a stretchable device and the stretchable device is applied in a position in which the fiber-based strain sensor is stretchable in a length direction.
8 . A monitoring system, comprising:
a fiber-based strain sensor including: at least one first electric conductive line including a first flexible part having electric conductivity and at least one second electric conductive line which is woven to be in partial contact with the at least one first electric conductive line, including a second flexible part having electric conductivity, and being implemented to conduct electricity with the first flexible part having electric conductivity in a stretched state;
a stretchable device to which the fiber-based strain sensor is applied and which is implemented to be stretchable by a motion; and
a monitoring device which receives current generated upon stretching in a wired or wireless method to monitor the state of the stretchable device,
wherein the at least one first electric conductive line and the at least one second electric conductive line form a physical structure comprising: a conductive part having electric conductivity formed by depositing metal nano particles inside the first flexible part and the second flexible part; and an insulator formed by depositing an insulating thin film on a surface of the conductive part,
wherein the at least one first electric conductive line and the at least one second electric conductive line are implemented with a negative gauge factor (N-GF) configured such that current flows as the at least one first electric conductive line and the at least one second electric conductive line directly contact each other through a crack formed by the insulator only in the stretched state, and
wherein a degree of causing a crack according to strain is adjusted by the insulating thin film having a preset modulus, thickness, or hardness through a curing process by selective irradiation of ultraviolet curing (UV-curing).
9 . The monitoring system according to claim 8 , wherein
the stretchable device is implemented to apply the fiber-based strain sensor in a position to be stretchable in a length direction so that the at least one first electric conductive line and the at least one second electric conductive line conduct electricity upon stretching and when the electricity is conducted by the stretching, the monitoring device predicts a shape of the stretchable device to provide a feedback in real time.